http://www.enr.gov.nt.ca/sites/defau...f_wildlife.pdf
This is what Canadian natives would eat so this is about real world accurate as you are going to get. Scale up from the Beluga whale edible weight listed which is 300-500 lbs per whale with a body weight of 2000 - 3000 lbs for about a 6 to 1 ratio. Blue whales are 100x as large so a 250,000 lb blue whale would yield about 40,000 lbs of edible meat-skin-fat. Assuming a calorie load of 37% meat 63% muktuk

whale meat (no fat is about 481 cals per lb -
Muktuk skin+fat is

2106 cals per lb
so 40,000 lbs x .37 = 14,800 lbs lean meat and x .63 = 25,200 lbs of muktuk

53,071,200 calories of muktuk +7,118,800 of lean meat = 60,190,000 edible calories in a blue whale / 2500 per day = 24,076 days or 65.96 years